Glossary definition of 'Bridge Tied Load'

(BTL) A technique for using two amplifiers connected in "bridged" mode to drive a single load in order to achieve an increased power output from a given voltage power supply. This is achieved by connecting the load between the positive terminals of two amplifiers and feeding one amplifier with an inverted version of the signal fed to the other.

In theory this should give 4x the output power of one of the amplifiers on its own (2x the voltage implies double the current, and therefore 4x the power), but in practice, since the power output of the individual channels is usually limited by their current capability, the output power is usually only doubled.